Fluval Hose Size: What 14.5mm and 17mm Actually Mean
Fluval states two hose sizes on its own product pages: 14.5mm for the 04 through 07 series canisters, and 17mm for the 304 through 407 series. Neither page says if that number is the inside or the outside of the hose.
That gap matters because an adapter needs the inside diameter to fit right. This guide shows exactly what Fluval states, why the number alone is not enough, and how to measure your own hose so you know your real size before you order anything.
What Fluval's own site says (14.5mm for 04-07 series, 17mm for 304-407 series)
Fluval's own product pages state two hose sizes, and only two, across its whole canister filter lineup.
Small and medium class filters use hose stated as 14.5mm. Large and XL class filters use hose stated as 17mm. Both numbers come straight from Fluval's own listed replacement hose parts, not a third party guess.
| Fluval filter series | Stated hose size | Fluval part number |
|---|---|---|
| 104/204, 105/205, 106/206, 107/207 (small and medium class) | 14.5mm | A20014 |
| 304/404, 305/405, 306/406, 307/407 (large and XL class) | 17mm | A20015 |
Sizes and part numbers come from Fluval's own USA product pages: https://fluvalaquatics.com/us/shop/product/ribbed-hosing-for-105-205-106-206-107-207-canister-filter-8-5-ft-2-5-m-l-x-14-5-mm for A20014, and https://fluvalaquatics.com/us/shop/product/ribbed-hosing-for-305-405-306-406-307-407-canister-filter-9-8-ft-3-m-l-x-17-mm for A20015. Two independent dealer pages state the same numbers. Fluval does not label either size as an inside or an outside diameter, and that is exactly why this size is not yet in our fitment data file. Full notes are in aquarium-fitment-verification-2026-07-10.md, Family 5.
Why that number alone does not tell you inside or outside diameter
An inside measurement and an outside measurement are not the same thing, and an adapter sized for one will not fit right if you needed the other.
This is not just a labeling headache. Buy a barb sized to 14.5mm as an inside measurement, and if the real number turns out to be the outside measurement, the barb will be too big to grip the hose at all. Get it backward the other way, and the barb will be too loose to hold a seal. Both mistakes are easy to make from a single unlabeled number.
We would rather tell you this plainly than guess and ship an adapter that does not fit. Until we measure a real piece of Fluval hose ourselves with calipers, we are not listing an inside or outside number as confirmed, and we do not sell a Fluval sized adapter.
| Measurement | What third party sellers state | Confidence |
|---|---|---|
| 17mm class inside diameter | 16mm to 17.8mm, depending on the seller | Low. Not Fluval's own number. |
| 17mm class outside diameter | 22.3mm to 22.4mm, depending on the seller | Low. Not Fluval's own number. |
These figures are not Fluval's own numbers. They come from third party Amazon listings, https://www.amazon.com/dp/B0FF8WS4SF and https://www.amazon.com/dp/B0FM7BXP6T among them, which disagree with each other and were not independently re-checked this pass. Treat them as a starting point only, not a confirmed size. We found even less third party data for the 14.5mm class, so we are not publishing a similar range for it. Full citations and confidence notes are in aquarium-fitment-verification-2026-07-10.md, Family 5.
How to measure your Fluval hose yourself
You do not need special tools. A soft tape measure, a small ruler, or a drill bit set works fine for checking your own hose.
- Measure the inside of the hose first. Ease a small rod, a drill bit, or the end of a tape measure gently into the opening until it just touches both sides.
- Write down the number in millimeters. If you only have an inch ruler, note the closest fraction of an inch and convert it later.
- Measure the outside next. Wrap a soft tape measure around the hose and divide the distance around by about 3.14, or measure straight across with calipers if you have them.
- Write both numbers down and label which is which. A hose that measures 14.5mm on the outside and one that measures 14.5mm on the inside are very different fits.
- Measure twice if you can. Hose flattens and stretches with use, so a number taken right off the filter can read differently once the hose relaxes.
Fluval's hose size tracks filter class, not the generation number
Hose size on a Fluval canister depends on which size class the filter belongs to, not which generation it is.
Every generation in the 104 through 207 small and medium class uses the same 14.5mm hose. Every generation in the 304 through 407 large and XL class uses the same 17mm hose. A 107 and a 104 take the same hose. A 307 and a 304 take the same hose. The two classes do not share a size with each other.
This matters if you are shopping for a used filter or a replacement hose and only know the model name. Check which class your model falls into first, then use the size that matches the class, not the generation number by itself.
Frequently asked questions
Is Fluval's 14.5mm hose size the inside or outside diameter?+
Fluval does not say. We have not confirmed it either, and we will not guess. Measure your own hose using the steps in this guide if you need to know for sure.
Do all Fluval 07 series filters use the same hose?+
Yes, within the same size class. A 107, 106, 105, and 104 all use the 14.5mm hose. The 307 and other large class models use the 17mm hose instead.
Will a 5/8 inch adapter fit my Fluval hose?+
We do not know yet, and we would rather say that than guess. Measure your hose first using the steps in this guide.
Does TankRig sell an adapter for Fluval hose?+
Not yet. The inside versus outside question is not settled, so we have not sized one. We are working on it.
Why do third party sellers list different sizes for the same Fluval hose?+
They are measuring or estimating on their own, and their numbers do not always agree with each other. None of them are official Fluval numbers, so we treat them as a starting point, not a confirmed size.
Is it safe to use a printed adapter on my Fluval filter?+
When we do sell one, it will be PETG, the material aquarium keepers have used submerged for years. Rinse any new printed part in clean water before it goes in your tank. We do not have a Fluval sized part yet.
A note on safety
We print every part in PETG. It is the material aquarium keepers have used submerged for years. We cannot promise how any part performs in your tank. You know your tank and your animals best, so the call is always yours. Rinse each part in clean water before you add it to your tank.